Soft magnetic properties and microstructure of high moment Fe-N-Al-O films for recording heads

Fe-N-Al-O alloy films were fabricated by rf reactive sputtering in a mixed Ar+N₂ plasma. The Al and O contents in films were varied by the area ratio of Al₂ O₃ chips placed on an Fe target. We examined the effects of additional elements, such as Al and O, on magnetic and electrical properties of the Fe-N-Al-O films, and we investigated the relationship between soft magnetic properties and microstructure. The permeability reaches a maximum of about 1800, when the Al+O content range is 10-16 at%. Fe-N-Al-O films in this range have 4πMs=19-20 kG and ρ = 60-100 μΩcm. The real part of permeability (μ′) of the 0.7-μm-thick Fe₇₉N₅Al₆O₁₀ film remains constant up to 300 MHz. The as-deposited Fe-N-Al-O film showing soft magnetic properties has homogeneous microstructure with a grain size of about 5 nm. It seems that the addition of Al and O to Fe-N films is effective in suppressing grain growth, and contributes to the formation of homogeneous film structure.